First, we create a maven project, as shown in the following figure:

Step 2: configure pom.xml

<parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.4.1.RELEASE</version>
  </parent>
<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <!-- Specify jdk We use jdk 1.7 ,The default is 1..6 -->
    <java.version>1.7</java.version>
  </properties>
  
  <dependencies>
          <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
   
    <!-- Add to fastjson Dependency package. -->
        <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.15</version>
        </dependency>
        
        <!-- spring boot devtools Dependency package. -->
        <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-devtools</artifactId>
           <optional>true</optional>
          <scope>true</scope>
        </dependency>
   
  </dependencies>

Step 3: create the package structure and class as shown in the following figure

Step 4: write the above three classes
User:

Provide get and set methods.
FastJsonController:

App:

After the above steps are completed, execute the main method of App class and wait for the project to start. Then access in the browser
http://localhost:8080/getJson, the returned result is as follows:

When Chinese code is found, modify the controller class, as shown in the following figure:

Then visit again, the results are as follows:

Solve the confusion.